Demagnetization Effect and Relaxation of a Magnetic Moment of YBa2Cu3O7-δ Film in Low Magnetic Field

Precise measurements of a magnetic moment relaxation of YBa2Cu3O7-δ film were carried out at temperature T = 32 K at the magnetic fields H ≤ 1600 Oe. The moment M, relaxation rates R = – dM / dln t and S = R / M as well as glassy exponent μ were analyzed in partly and fully penetrated critical state in dependence on increasing and decreasing field. We demonstrated that a demagnetization affects the magnetic moment and the rate R but it does not influence on the normalized rate S and μ. Obtained value μ ≈ 1 and observed suppression of the critical current by the magnetic field evince creep of small bundles of vortices.